1. Technical Field
This invention relates to methods for monitoring and determining fuel economy in motor vehicles, and more particularly to a method for monitoring and determining fuel economy of a motor vehicle having a gasoline powered engine.
2. Discussion
Present day motor vehicle such as automobiles, trucks, vans, etc., make use of various methods for determining fuel economy of the vehicle. Some methods even provide an approximation of the instantaneous fuel economy of the vehicle. However, certain drawbacks exist with present day methods for obtaining an average fuel economy.
Most present day methods for obtaining an average fuel economy typically make use of algorithms which utilize fuel-used estimations. The fuel-used estimations are based on the accumulated time which each fuel injector of the engine of the vehicle is turned on. The injectors are further assumed to be operating under static pressure conditions, that is, conditions which do not result in an appreciable change in the amount of fuel flowing through the injectors. Thus, various factors such as wind resistance encountered by the vehicle, the road the vehicle is traveling on, vehicle speed, engine rpm, fuel temperature, fuel octane, etc., are not taken into account by previously developed fuel economy estimation methods. Thus, current approaches for estimating fuel economy do not take into account the various dynamic variables that can significantly influence the vehicle's fuel economy. This can result in a significant degree of error, sometimes as much as 10% or greater, in the estimated fuel economy of the vehicle.
Accordingly, it would be highly desirable to provide a method for more accurately determining the fuel economy of a gasoline powered motor vehicle. More specifically, it would be highly desirable to provide a method for taking into account the numerous dynamic variables such as engine rpm, vehicle speed, fuel temperature, fuel octane and other variables which have a definite influence on the instantaneous fuel economy of the vehicle. It would further be desirable if such a method could be provided which enables the above-mentioned variables to be taken into account while providing an accurate fuel economy value, in real time, such that a driver or operator of a vehicle can monitor the instantaneous fuel economy of the vehicle.